No one is at zero risk for stroke, which explains why it is vital to know the signs and understand how to decrease the chance of experiencing a stroke.

Current therapies are powerful and effective, but can be applied only in the first few hours, said Dr. Dennis Landis, chair of neurology at Baylor College of Medicine in Houston.

Good cardiovascular health habits greatly reduce the risk of stroke. Hypertension and diabetes must be recognized and treated. Smoking, obesity and lack of exercise all increase the risk of stroke, but that risk is reduced when a person modifies those habits.

A stroke is caused by loss of blood supply to a portion of the brain which results in loss of brain function. For example, loss of blood supply to the portion of the brain controlling movement may result in paralysis of the arm and leg. Landis stresses the importance of acting on the following warning signs and seeking emergency care immediately:

 Sudden numbness or weakness affecting the face, arm or leg, especially on one side of the body.

 Sudden difficulty in speaking or understanding speech.

 Sudden trouble seeing in one or both eyes.

 Sudden trouble walking, dizziness, loss of balance or coordination.

At a certified stroke center, a Brain Attack team of specially trained physicians and nurses can rapidly determine whether a stroke is in progress, and whether to treat it with clot-busting medications. A stroke can be stopped in its tracks in the first few hours with clot-busting medications.

Nearly half of strokes are preceded by transient symptoms or signs. These are warnings of disaster. Even though a person may seem to recover in minutes, they should go directly to an emergency facility for diagnosis and help.

Some ischemic strokes may seem to cause only minimal damage, but they are still important.

"If you have a block in a small blood vessel irrigating a portion of the white matter in the frontal lobe, the symptoms may be subtle. Don't ignore the minor problem," said Landis. "Diseases like diabetes and hypertension are also causing damage in similar vessels elsewhere. A block in an equally small blood vessel that serves the portion of the brain responsible for motor activity can cause a person to be paralyzed."

Stroke victims can recover partial or complete loss of motor or speech function because of other areas of the brain that take over, but dead brain cells cannot be resurrected. The promise of stem cell therapy to re-grow brain tissue lost from stroke is distant at present, said Landis, although there have been several recent advances in post-stroke therapy.

If a person is forced to use the weak limb in the early days after stroke by restraining the normal limb, the chances of recovering function are increased. Direct electrical stimulation of muscles in paralyzed limbs can be used to elicit nearly normal movement, and may bolster the recovery of normal control.

"We're getting better and better with preventive and treatment techniques," said Landis. "Even more exciting is that there are now many therapies that can greatly reduce the risk of stroke."